Generally, in a network device, various circuit elements are interconnected in order to filter, mix, amplify, and convert signals. There may be multiple stages of filtering and amplification in a signal's path, and each stage may contribute some offset voltage (e.g., error) to the signal as it is modified along the circuit. A variable gain amplifier (VGA) may be used in a signal's path (e.g., at a last stage of the path). The VGA may take a differential input signal (e.g., as modified by previous circuit elements in the path) and output an amplified differential signal or an amplified single ended signal
However, the differential input signal may include an offset voltage of the signal path (e.g., error generated along the signal path). The VGA may also contribute an internal offset voltage to the signal. These offset voltages, if uncorrected, may be amplified by the VGA and reduce the usable amplitude range of the VGA output. Thus, calibration of the signal is desirable to counteract both the offset voltage of the input signal as well as the offset voltage internal to the VGA.
Calibration may include determining the offset voltage of the signal path and the offset voltage of the VGA. For example, the output of the VGA may be swept over its entire range while applying an offset correction voltage to the VGA until the output crosses zero. Alternatively, a binary or intelligent search may be conducted to arrive at these offset voltages. However, these methods require taking a large range of measurements, which may be time intensive and costly.